The functions of the Clinical Core Laboratory will be: 1. to provide Individual Project #2 with access to accurate and reproducible measurements of a number of hormones and peptides that are markers of circadian rhythmicity, sleep and aging and are therefore important in the study of human diurnal rhythms in the elderly. The laboratory will utilize the existing facilities of its Principal Investigator, Dr. Polonsky and Co-Principal investigator, Dr. Refetoff at the University of Chicago. Both investigators have extensive experience in performing such measurements for circadian rhythm studies. The availability of the major items of equipment needed to perform these measurements will reduce the overall cost of these services to the Program Project and will ensure that they will perform in a cost effective manner. 2. to centralize the processing of the blood and urine samples collected in the course of screening and follow-up procedures for the subjects enlisted in Individual Project #1 who will be living in two different nursing homes in the Chicago area and those enlisted in Individual Project #2 who will be studied in the Clinical Research Center of the University of Chicago Hospitals. The Clinical Core Laboratory will keep detailed records on each subject. The selection process for subjects in Projects #1 and #2 will include measurements on blood and urine samples designed to screen pathological states and obtain detailed clinical data. To standardize these measurements, they will all be performed in the Clinical Laboratories of the University of Chicago. The staff of the Clinical Core Laboratory will ensure that the samples get adequately processed and will centralize the results.